When a transmitter transmits data in a transmission control protocol (TCP) layer, data is transmitted through hybrid automatic retransmit request (HARQ). When an error is generated in the HARQ step, the transmitter receives feedback of TCP ACK/NACK in the TCP layer and retransmits the data.
In typical data transmission, HARQ data is transmitted while maintaining a block error rate (BLER) of 10%. When a data transmission error is generated, the transmitter retransmits through HARQ retransmission and a receiver recovers an error by combining previously received data and the retransmitted data. As described, a typical data transmission scheme sends an appropriate amount of redundancy data and retransmits data upon the generation of a data transmission error rather than unconditionally transmitting a large amount of redundancy data for successful transmission.
TCP transmission performs flow control on the basis of a sliding window that enables forward data transmission only when ACK/NACK is received from the receiver. However, when the BLER of HARQ transmission is set to 10%, HARQ retransmission may occur twice or three times for a certain packet. If a TCP ACK/NACK packet is retransmitted twice or three times in the HARQ step, the transmitter waits for transmission of next data until the TCP ACK/NACK packet is received, resulting in transmission rate decrease. Specifically, if retransmission occurs twice or three times when HARQ RTT (Round Trip Time) is about 8 ms in LTE (Long Term Evolution), TCP ACK information is transmitted with a delay of about 16 to 24 ms.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.